diff --git a/cmd/tui/selector.go b/cmd/tui/selector.go
index 898c1396d..7bf8180be 100644
--- a/cmd/tui/selector.go
+++ b/cmd/tui/selector.go
@@ -415,6 +415,12 @@ type multiSelectorModel struct {
 	cancelled    bool
 	confirmed    bool
 	width        int
+
+	// multi enables full multi-select editing mode. The zero value (false)
+	// shows a single-select picker where Enter adds the chosen model to
+	// the existing list. Tab toggles between modes.
+	multi     bool
+	singleAdd string // model picked in single mode
 }
 
 func newMultiSelectorModel(title string, items []SelectItem, preChecked []string) multiSelectorModel {
@@ -429,13 +435,23 @@ func newMultiSelectorModel(title string, items []SelectItem, preChecked []string
 		m.itemIndex[item.Name] = i
 	}
 
-	for _, name := range preChecked {
-		if idx, ok := m.itemIndex[name]; ok {
+	// Reverse order so preChecked[0] (the current default) ends up last
+	// in checkOrder, matching the "last checked = default" convention.
+	for i := len(preChecked) - 1; i >= 0; i-- {
+		if idx, ok := m.itemIndex[preChecked[i]]; ok {
 			m.checked[idx] = true
 			m.checkOrder = append(m.checkOrder, idx)
 		}
 	}
 
+	// Position cursor on the current default model
+	if len(preChecked) > 0 {
+		if idx, ok := m.itemIndex[preChecked[0]]; ok {
+			m.cursor = idx
+			m.updateScroll(m.otherStart())
+		}
+	}
+
 	return m
 }
 
@@ -546,14 +562,25 @@ func (m multiSelectorModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			m.cancelled = true
 			return m, tea.Quit
 
+		case tea.KeyTab:
+			m.multi = !m.multi
+
 		case tea.KeyEnter:
-			if len(m.checkOrder) > 0 {
+			if !m.multi {
+				if len(filtered) > 0 && m.cursor < len(filtered) {
+					m.singleAdd = filtered[m.cursor].Name
+					m.confirmed = true
+					return m, tea.Quit
+				}
+			} else if len(m.checkOrder) > 0 {
 				m.confirmed = true
 				return m, tea.Quit
 			}
 
 		case tea.KeySpace:
-			m.toggleItem()
+			if m.multi {
+				m.toggleItem()
+			}
 
 		case tea.KeyUp:
 			if m.cursor > 0 {
@@ -592,7 +619,9 @@ func (m multiSelectorModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			// On some terminals (e.g. Windows PowerShell), space arrives as
 			// KeyRunes instead of KeySpace. Intercept it so toggle still works.
 			if len(msg.Runes) == 1 && msg.Runes[0] == ' ' {
-				m.toggleItem()
+				if m.multi {
+					m.toggleItem()
+				}
 			} else {
 				m.filter += string(msg.Runes)
 				m.cursor = 0
@@ -604,6 +633,19 @@ func (m multiSelectorModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	return m, nil
 }
 
+func (m multiSelectorModel) renderSingleItem(s *strings.Builder, item SelectItem, idx int) {
+	if idx == m.cursor {
+		s.WriteString(selectorSelectedItemStyle.Render("▸ " + item.Name))
+	} else {
+		s.WriteString(selectorItemStyle.Render(item.Name))
+	}
+	s.WriteString("\n")
+	if item.Description != "" {
+		s.WriteString(selectorDescLineStyle.Render(item.Description))
+		s.WriteString("\n")
+	}
+}
+
 func (m multiSelectorModel) renderMultiItem(s *strings.Builder, item SelectItem, idx int) {
 	origIdx := m.itemIndex[item.Name]
 
@@ -615,7 +657,7 @@ func (m multiSelectorModel) renderMultiItem(s *strings.Builder, item SelectItem,
 	}
 
 	suffix := ""
-	if len(m.checkOrder) > 0 && m.checkOrder[0] == origIdx {
+	if len(m.checkOrder) > 0 && m.checkOrder[len(m.checkOrder)-1] == origIdx {
 		suffix = " " + selectorDefaultTagStyle.Render("(default)")
 	}
 
@@ -637,6 +679,11 @@ func (m multiSelectorModel) View() string {
 		return ""
 	}
 
+	renderItem := m.renderSingleItem
+	if m.multi {
+		renderItem = m.renderMultiItem
+	}
+
 	var s strings.Builder
 
 	s.WriteString(selectorTitleStyle.Render(m.title))
@@ -661,7 +708,7 @@ func (m multiSelectorModel) View() string {
 			if idx >= len(filtered) {
 				break
 			}
-			m.renderMultiItem(&s, filtered[idx], idx)
+			renderItem(&s, filtered[idx], idx)
 		}
 
 		if remaining := len(filtered) - m.scrollOffset - displayCount; remaining > 0 {
@@ -684,7 +731,7 @@ func (m multiSelectorModel) View() string {
 			s.WriteString(sectionHeaderStyle.Render("Recommended"))
 			s.WriteString("\n")
 			for _, idx := range recItems {
-				m.renderMultiItem(&s, filtered[idx], idx)
+				renderItem(&s, filtered[idx], idx)
 			}
 		}
 
@@ -704,7 +751,7 @@ func (m multiSelectorModel) View() string {
 				if idx >= len(otherItems) {
 					break
 				}
-				m.renderMultiItem(&s, filtered[otherItems[idx]], otherItems[idx])
+				renderItem(&s, filtered[otherItems[idx]], otherItems[idx])
 			}
 
 			if remaining := len(otherItems) - m.scrollOffset - displayCount; remaining > 0 {
@@ -716,15 +763,18 @@ func (m multiSelectorModel) View() string {
 
 	s.WriteString("\n")
 
-	count := m.selectedCount()
-	if count == 0 {
-		s.WriteString(selectorDescStyle.Render("  Select at least one model."))
+	if !m.multi {
+		s.WriteString(selectorHelpStyle.Render("↑/↓ navigate • enter select • tab add multiple • esc cancel"))
 	} else {
-		s.WriteString(selectorDescStyle.Render(fmt.Sprintf("  %d selected - press enter to continue", count)))
+		count := m.selectedCount()
+		if count == 0 {
+			s.WriteString(selectorDescStyle.Render("  Select at least one model."))
+		} else {
+			s.WriteString(selectorDescStyle.Render(fmt.Sprintf("  %d selected - press enter to continue", count)))
+		}
+		s.WriteString("\n\n")
+		s.WriteString(selectorHelpStyle.Render("↑/↓ navigate • space toggle • tab select single • enter confirm • esc cancel"))
 	}
-	s.WriteString("\n\n")
-
-	s.WriteString(selectorHelpStyle.Render("↑/↓ navigate • space toggle • enter confirm • esc cancel"))
 
 	result := s.String()
 	if m.width > 0 {
@@ -747,18 +797,28 @@ func SelectMultiple(title string, items []SelectItem, preChecked []string) ([]st
 	}
 
 	fm := finalModel.(multiSelectorModel)
-	if fm.cancelled {
+	if fm.cancelled || !fm.confirmed {
 		return nil, ErrCancelled
 	}
 
-	if !fm.confirmed {
-		return nil, ErrCancelled
+	// Single-add mode: prepend the picked model, keep existing models deduped
+	if fm.singleAdd != "" {
+		result := []string{fm.singleAdd}
+		for _, name := range preChecked {
+			if name != fm.singleAdd {
+				result = append(result, name)
+			}
+		}
+		return result, nil
 	}
 
-	var result []string
+	// Multi-edit mode: last checked is default (first in result)
+	last := fm.checkOrder[len(fm.checkOrder)-1]
+	result := []string{fm.items[last].Name}
 	for _, idx := range fm.checkOrder {
-		result = append(result, fm.items[idx].Name)
+		if idx != last {
+			result = append(result, fm.items[idx].Name)
+		}
 	}
-
 	return result, nil
 }
diff --git a/cmd/tui/selector_test.go b/cmd/tui/selector_test.go
index f87b57aac..fa8ff4dc4 100644
--- a/cmd/tui/selector_test.go
+++ b/cmd/tui/selector_test.go
@@ -539,6 +539,7 @@ func TestMultiView_CursorIndicator(t *testing.T) {
 
 func TestMultiView_CheckedItemShowsX(t *testing.T) {
 	m := newMultiSelectorModel("Pick:", items("a", "b"), []string{"a"})
+	m.multi = true
 	content := m.View()
 
 	if !strings.Contains(content, "[x]") {
@@ -550,11 +551,18 @@ func TestMultiView_CheckedItemShowsX(t *testing.T) {
 }
 
 func TestMultiView_DefaultTag(t *testing.T) {
-	m := newMultiSelectorModel("Pick:", items("a", "b"), []string{"a"})
+	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), []string{"a", "b"})
+	m.multi = true
 	content := m.View()
 
 	if !strings.Contains(content, "(default)") {
-		t.Error("first checked item should have (default) tag")
+		t.Error("should have (default) tag")
+	}
+	// preChecked[0] ("a") should be the default (last in checkOrder)
+	aIdx := strings.Index(content, "a")
+	defaultIdx := strings.Index(content, "(default)")
+	if defaultIdx < aIdx {
+		t.Error("(default) tag should appear after 'a' (the current default)")
 	}
 }
 
@@ -585,6 +593,7 @@ func TestMultiView_OverflowIndicator(t *testing.T) {
 
 func TestMultiUpdate_SpaceTogglesItem(t *testing.T) {
 	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), nil)
+	m.multi = true
 	m.cursor = 1
 
 	// Simulate space delivered as tea.KeySpace
@@ -601,6 +610,7 @@ func TestMultiUpdate_SpaceTogglesItem(t *testing.T) {
 
 func TestMultiUpdate_SpaceRuneTogglesItem(t *testing.T) {
 	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), nil)
+	m.multi = true
 	m.cursor = 1
 
 	// Simulate space delivered as tea.KeyRunes (Windows PowerShell behavior)
@@ -618,6 +628,161 @@ func TestMultiUpdate_SpaceRuneTogglesItem(t *testing.T) {
 	}
 }
 
+// --- Single-add mode ---
+
+func TestMulti_StartsInSingleMode(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b"), nil)
+	if m.multi {
+		t.Error("should start in single mode (multi=false)")
+	}
+}
+
+func TestMulti_SingleModeNoCheckboxes(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b"), nil)
+	content := m.View()
+	if strings.Contains(content, "[x]") || strings.Contains(content, "[ ]") {
+		t.Error("single mode should not show checkboxes")
+	}
+	if !strings.Contains(content, "▸") {
+		t.Error("single mode should show cursor indicator")
+	}
+}
+
+func TestMulti_SingleModeEnterPicksItem(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), nil)
+	m.cursor = 1
+
+	updated, _ := m.Update(tea.KeyMsg{Type: tea.KeyEnter})
+	m = updated.(multiSelectorModel)
+
+	if m.singleAdd != "b" {
+		t.Errorf("enter in single mode should pick cursor item, got %q", m.singleAdd)
+	}
+	if !m.confirmed {
+		t.Error("should set confirmed")
+	}
+}
+
+func TestMulti_SingleModeSpaceIsNoop(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b"), nil)
+	m.cursor = 0
+
+	updated, _ := m.Update(tea.KeyMsg{Type: tea.KeySpace})
+	m = updated.(multiSelectorModel)
+
+	if len(m.checked) != 0 {
+		t.Error("space in single mode should not toggle items")
+	}
+}
+
+func TestMulti_SingleModeSpaceRuneIsNoop(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b"), nil)
+	m.cursor = 0
+
+	updated, _ := m.Update(tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{' '}})
+	m = updated.(multiSelectorModel)
+
+	if len(m.checked) != 0 {
+		t.Error("space rune in single mode should not toggle items")
+	}
+	if m.filter != "" {
+		t.Error("space rune in single mode should not add to filter")
+	}
+}
+
+func TestMulti_TabTogglesMode(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a", "b"), nil)
+
+	if m.multi {
+		t.Fatal("should start in single mode")
+	}
+
+	updated, _ := m.Update(tea.KeyMsg{Type: tea.KeyTab})
+	m = updated.(multiSelectorModel)
+	if !m.multi {
+		t.Error("tab should switch to multi mode")
+	}
+
+	updated, _ = m.Update(tea.KeyMsg{Type: tea.KeyTab})
+	m = updated.(multiSelectorModel)
+	if m.multi {
+		t.Error("tab should switch back to single mode")
+	}
+}
+
+func TestMulti_SingleModeHelpText(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a"), nil)
+	content := m.View()
+	if !strings.Contains(content, "tab add multiple") {
+		t.Error("single mode should show 'tab add multiple' in help")
+	}
+}
+
+func TestMulti_MultiModeHelpText(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("a"), nil)
+	m.multi = true
+	content := m.View()
+	if !strings.Contains(content, "tab select single") {
+		t.Error("multi mode should show 'tab select single' in help")
+	}
+}
+
+// --- preChecked initialization order ---
+
+func TestMulti_PreCheckedDefaultIsLast(t *testing.T) {
+	// preChecked[0] ("a") is the current default and should end up
+	// last in checkOrder so it gets the (default) tag.
+	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), []string{"a", "b", "c"})
+
+	if len(m.checkOrder) != 3 {
+		t.Fatalf("expected 3 in checkOrder, got %d", len(m.checkOrder))
+	}
+	lastIdx := m.checkOrder[len(m.checkOrder)-1]
+	if m.items[lastIdx].Name != "a" {
+		t.Errorf("preChecked[0] should be last in checkOrder, got %q", m.items[lastIdx].Name)
+	}
+}
+
+func TestMulti_CursorOnDefaultModel(t *testing.T) {
+	// preChecked[0] ("b") is the default; cursor should start on it
+	m := newMultiSelectorModel("Pick:", items("a", "b", "c"), []string{"b", "c"})
+
+	if m.cursor != 1 {
+		t.Errorf("cursor should be on preChecked[0] ('b') at index 1, got %d", m.cursor)
+	}
+}
+
+// --- Multi-mode last-checked is default ---
+
+func TestMulti_LastCheckedIsDefault(t *testing.T) {
+	m := newMultiSelectorModel("Pick:", items("alpha", "beta", "gamma"), nil)
+	m.multi = true
+
+	// Check "alpha" then "gamma"
+	m.cursor = 0
+	m.toggleItem()
+	m.cursor = 2
+	m.toggleItem()
+
+	// Last checked ("gamma") should be at the end of checkOrder
+	lastIdx := m.checkOrder[len(m.checkOrder)-1]
+	if m.items[lastIdx].Name != "gamma" {
+		t.Errorf("last checked should be 'gamma', got %q", m.items[lastIdx].Name)
+	}
+
+	// The (default) tag renders based on checkOrder[len-1]
+	content := m.View()
+	if !strings.Contains(content, "(default)") {
+		t.Fatal("should show (default) tag")
+	}
+	// "alpha" line should NOT have the default tag
+	for _, line := range strings.Split(content, "\n") {
+		if strings.Contains(line, "alpha") && strings.Contains(line, "(default)") {
+			t.Error("'alpha' (first checked) should not have (default) tag")
+		}
+	}
+}
+
 // Key message helpers for testing
 
 type keyType = int
diff --git a/cmd/tui/tui.go b/cmd/tui/tui.go
index 932af312c..b9f1ef7b1 100644
--- a/cmd/tui/tui.go
+++ b/cmd/tui/tui.go
@@ -429,8 +429,24 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			}
 			if m.multiModalSelector.confirmed {
 				var selected []string
-				for _, idx := range m.multiModalSelector.checkOrder {
-					selected = append(selected, m.multiModalSelector.items[idx].Name)
+				if m.multiModalSelector.singleAdd != "" {
+					// Single-add mode: prepend picked model, keep existing deduped
+					selected = []string{m.multiModalSelector.singleAdd}
+					for _, name := range config.IntegrationModels(m.items[m.cursor].integration) {
+						if name != m.multiModalSelector.singleAdd {
+							selected = append(selected, name)
+						}
+					}
+				} else {
+					// Last checked is default (first in result)
+					co := m.multiModalSelector.checkOrder
+					last := co[len(co)-1]
+					selected = []string{m.multiModalSelector.items[last].Name}
+					for _, idx := range co {
+						if idx != last {
+							selected = append(selected, m.multiModalSelector.items[idx].Name)
+						}
+					}
 				}
 				if len(selected) > 0 {
 					m.changeModels = selected